Enoxaparin Dosing in STEMI
For patients with STEMI, enoxaparin should be dosed as follows: patients under 75 years should receive a 30 mg IV bolus followed by 1 mg/kg subcutaneously every 12 hours (maximum 100 mg for first 2 doses), while patients 75 years or older should receive no IV bolus and 0.75 mg/kg subcutaneously every 12 hours (maximum 75 mg for first 2 doses). 1
Age-Based Dosing Algorithm
Patients < 75 years:
- Initial dose: 30 mg IV bolus
- Followed 15 minutes later by: 1 mg/kg subcutaneously every 12 hours
- Maximum dose: 100 mg for the first 2 subcutaneous doses
Patients ≥ 75 years:
- No IV bolus
- Initial dose: 0.75 mg/kg subcutaneously every 12 hours
- Maximum dose: 75 mg for the first 2 subcutaneous doses
Renal Adjustment
- For patients with impaired renal function (creatinine clearance < 30 mL/min):
- 1 mg/kg subcutaneously once daily (every 24 hours)
- Regardless of age 1
Duration of Therapy
Enoxaparin should be continued for:
- The duration of the index hospitalization
- Up to 8 days
- Or until revascularization is performed, whichever comes first 1
Clinical Context
The dosing regimen is supported by high-quality evidence from multiple guidelines and clinical trials. The 2013 ACCF/AHA guidelines for STEMI management provide a Class I, Level of Evidence A recommendation for this dosing strategy 1. This regimen has been shown to reduce mortality and recurrent myocardial infarction compared to unfractionated heparin in patients receiving fibrinolytic therapy 2, 3.
Important Considerations
- Do not switch between enoxaparin and unfractionated heparin due to increased bleeding risk 1
- For patients undergoing PCI who received enoxaparin within the prior 8 hours, no additional enoxaparin should be given 1
- If the last subcutaneous dose was administered 8-12 hours earlier before PCI, an IV dose of 0.3 mg/kg should be given 1
Monitoring and Safety
- Major bleeding complications are comparable to unfractionated heparin when appropriate dosing is used 2, 4
- Routine monitoring of anti-Xa levels is not required for most patients
- Careful attention to dosing is essential, particularly in elderly patients and those with renal impairment, to minimize bleeding risk
This evidence-based dosing regimen has been shown to improve outcomes in STEMI patients while maintaining an acceptable safety profile when properly administered according to patient characteristics.